Luminescent device



April 5, 1938 A. N.Luc|AN LUMINESCENT DEVICE 2 Sheets-sheet 1 Filed Dec.3l, 1954 Aprils, 193s. A. N. LUCIAN y 2,112,854

l LUMINESCENT DEVICE Fired Dec. '31, 1954 2 sheets-sheet 2 HE/mgggINVENTOR .Arum N. Lamar;A

AT ToRN EY.; y

Patented Apr. l5,1938

UNITEDv STATES PATENT Aorlucr;

, LUMINESCENT DEVICE Application December 31, 1934, Serial No. 759,836

13 Claims.

This invention involves the use of cathde ray I or electron deviceshaving luminescent screens for the purpose of providing commerciallyuseful lighting devices designed and constructed in accordance with theprinciples of luminescence phenomena, which term as employed in thiscase, includes phosphorescence, fluorescence, and allied phenomena whichmay be caused by the excitation of certain natural or syntheticcompounds by heat, light, cathode rays, X-rays, ra-

dium rays, and the like.

An object o f this invention is to provide commercially new and usefulcombinations based particularly upon cathode ray or electron excitationof luminescent compounds arranged to form display or advertising devicesand light sources.

A specific object of this invention is to provide constructions of'cathode, anode and a plurality of extended surfaces in such geometricalrelation to each other, so that the Surfaces to be illuminated will beuniformly irradiated by the action of a` uniforml;r disposed beam ofelectrons or cathode rays.

Another object of this invention is to provide in combination withdevices of this type, and as parts thereof, alternating currentrectifiers which directly supply the rectied current for the operationof the device.

Another object is to provide adequate and reliable pressure regulatingmeans in combination with devices of this type, and as parts thereof inorder to give to such devices long and uniform life of operation.

Other objects of this invention are- To provide a luminous device foradvertising purposes in which the areas to be impressed upon or broughtto the observers attention are completely luminous in themselves, andthese areas supply all the lightl used in illuminating the sign or otheradvertising device. l

To provide a source of illumination more emcient as regards the ratio ofcurrent consumption to quantity of light produced than any otherilluminating device of which I amaware.

To provide a source of illumination which emits light of practically anydesired color being generated on a luminous areaof such extent thatThese and many other objects, as will4 appear from the followingdetailed disclosure, are successfully secured'by meansof this invention.

In the drawings, l

Fig. 1 illustrates a cathode ray excited luminescent device of a formnow generally known and illustrating the basic features of devices ofAthis nature;

Fig. 2 is one form of the device in accordance with this inventionemploying a cold cathode;

llig. 3 is a detailed cross-sectional view of an element of theinvention;

Fig. 4 is a view illustrating the application of the principles of thisinvention to the hot cathode' type of tube; Y

Flg.5 is a top plan view of l a commercially practical form ofadvertising or display device in accordance with this invention andembodying as a part thereof a halfway rectifier;

Fig. 6 is a front elevational-view of this device;

. Fig. 7 is a top plan view of a modified form of device in which afull-way rectier is incorporated;

Fig. 8 is a front elevational View of a still further modification inaccordance with this invention; A

` Fig. 9 is a central vertical cross-sectional view 4of the device ofFig. 8;

Fig. 10 is a plan view of a modified form of device in accordance withthis invention particularly adapted as a light source; y

Fig. 11 is a still further modified form employing a. dome-shapedvessel.

Cathode' vray devices employing luminescent materials .have-been knownscientifically and in the laboratory for at least half a century. Verylittle practical and commercial use has been made of this device. Thewell known X-ray screen which has been highly developed, is in no sensein the samecategory and is not governed by the same considerations andphysical and chemical laws as the cathode ray device. lIn the AX-raydevice a luminescent screen is frequently employed wherein this screenis external to the tube in which the X-rays are generated and which, ofcourse,-is excited by X-rays. Furthermore, many `substances whichrespond to X-rays will not re spond to cathode rays and vice versa.

The only .commercially useful forms of cathode ray tubes 'are thecathode ray oscillograph and a modification thereof as employed intelevision. The cathode ray `oscillograph may or may not employ aluminescent screen. For example, through thel use of a Lenard window thecathode ray beam may be projected upon a photographic and purpose ofthis invention is to accomplish plate or upon a screen for use, forexample, in

visually displaying the voltage and current characteristics of electriccurrents. As employed in television apparatus the cathode ray tubeemploys a luminescent screen over which a concentrated beam oi'electrons is caused tov travel by and in accordance with electriccurrents or impulses representative of a scene whereby those currentsare transformed into visible displays of the scene. v Y

The distinctive object of the present invention is to disclose a newtype of vacuum tube, for the purpose of uniformly exciting, withouticker and fluctuation, large areas of luminescent materials which havebeen arranged in 4accordance with predetermined color and shapecombinations to provide advertising and display devices or to providethese objects;

In furtherance of these objects the present invention provides a devicehaving a life comparable with filament types of light sources and gasdischarge types of light sources.

A luminescent light source is one which emits light of practically anydesired color by the conversion of cathode ray or other radiations ofshorter wave length than red iight into visible light while generatingvery little heat; that heat which is generated not being usedas a sourceof light.

While the cathode ray luminescent device is well known scientifically,it may be of hei'p" to briey described in connection with Fig. 1, thefundamental principles involved. The device employs usually a glassenvelope I having a hot or cold cathode 2, and an anode 3 mountedtherein. Such devices usually contain a. residual of rareed gas, in theuse of cold cathodes, such as air or other desirable gas in which thedischarge takes place between the electrodes. The application ofpotentials across the electrodes sets the gas molecules in motion,causing collisions'which break the molecules up into positive andnegative ions. The passage of current through the device is accomplishedby fthe movement of the positive ions toward the cathode and of thenegative ions toward the anode. ions upon the cathode surface causes theejection of electrons or cathode particles, which in turn travel at highvelocities in straight lines at right angles to the surface of thecathode. If any one ofl a large number of known chemical comcompoundwill become luminescent.

'mostly by scientists have always been characterized by the fact thatthe area of th layer 5 has been extremely limited, thus generallykeeping the device out of the field of commercial utility. Furthermore,uniformity of illumination of the The impact of the positive.

surface has ybeen'entirely lacking, which, added to the fact that suchdevices have had an extremely short life, 'has prevented them enteringuseful fields aside from the cathode ray oscillograph, and even in thiscase the life of the device is unduly short. In accordance with thisinvention, in adapting the device for the intended purposes, certaindefinite combinations and control factors have been discovered whichmust be employed in the device.

The nature of ,the cathode and anode materials and the areas of thecooperating electrodes are important factors in developing acommercially useful lightingor display source. 'I'he electro-l positiveelements are the most suitable and eficientv materials of which to makethe electrodes and of which sodium, potassium, barium, strontium,calcium, magnesium and aluminum are examples. 'I'hese elements may beused individually or in any suitable combination. Apreferred-combination is an alloy of aluminum, magnesium and calciumwith traces of barium and strontium.

An important feature of the present invention lresides in the form,shape, size and position of the cathode to secure uniformity ofirradiation of the luminescent surface. jected area of the cathodeshould coincide with the area of said surface. Y

Furthermore, it has been discovered that the electrode area (referringto anode) in relation to the current density is important. In accordancewith this invention it has been found that a current density of lmilliampere for an-electrode area of 0.2 to 0.5 square centimeter issatisfactory. The minimum value holds particularly where the electrodesare not artificially cooled and where one electrode must act as anelement of the rectifier. Larger current densities may be employed incases where the device is-artiiiciall-y cooled, depending somewhat upc-nthe design of the cooling system.

Other important factors in the correct Yoperation of a device of thistype involve the nature of the rareed atmosphere within the vessel aswell as the pressure thereof. In addition to residual air, andpreferably the so-called noble gases, such as argon, neon'and helium,may be employed, either singly or in combination.I Likewise', hydrogen,nitrogen and carbon dioxide, either alone or in combination,` may. beemployed sometimes.

'The pressure range is, of course, variable, de-

pending upon the nature of the gas, the dimen.

sions of the device, and the potentials at which it is desired tooperate the device. Asv a working range, the pressure within the vesselwould be from approximately 0.1 millimeter of mercury down to as low apressure as is permissible with a particular operating potential. Forexample, a pressure of 0.001 millimeter of mercury representsl apractical minimum value for the range of potentials to be preferablyemployed. With cold cathode tubes potentials ranging from 1000 voltsupwards to 25,000 -volts are suitable. The above pressure range is notused vin any cathode ray orelectron device now in commercial use.

'I'hese devices may be operatedvfrom energy sources having a rather widefrequency range of the order of from a direct Vcurrent of zeroy vices ofthis type must be energized by high potential directcurrent, specialprovision for the supply of such current must be made as the availablecommercial current sources do not have the.

sur

' cathode ray device referred to above as used by the scientist. Thisproblem is solved by the invention by combining in a single device acathode ray irradiated luminescent surface and a half or full waverectifier by a novel arrangement and circuit interconnection ofelectrodes. Where high frequency currents are used a high .intensity ofluminescence may be secured with a high frequency source connected toelectrodes external to the vessel. Likewise, eilicient excitation may beobtained through a combinationof electrodes external and internal to thevessel. It is understood that in case of high frequency excitationproper safeguard must be used to eliminate loss of power by leakage.'

There is, of course, a very wide range of luminescent materials orcompounds that may 'be employed. By way of example only, kunzites,

calcites, sulphides 'of zinc, cadmium, barium, strontium and calcium,willemite, cadmium tungstate, calcium tungstate, uranyl salts, metallicsalicylates, calcium larsenite, and the like, arey available.

A feature of the invention insuring constancy and uniformity ofoperation is illustrated in Fig. 2. wherein at E is shown the vesselhaving a rare-h fied atmosphere within which is mounted ,the

cold cathode 'l and an anode 8. Intermediate to uctuate with the age ofthe device and par- Y ticularly at the beginning of its useful, life.The

' tendency is for the tube to. become "hard", that is, a .decrease inthe pressure within the tube which may be restored by means of asuitable pressure regulating device indicated generally by the referencenumeral Il. Such a devicemay be, although not necessarily, of the formdisclosed in Patent No. 1,603,707, to Lucian, dated October 1'9, 1926.For the purposes of the present disclosure the regulating deviceconsists of a porous thimble l2 within an extension i 5 of thevesseltcontaining a suitable chemical compound i3 a'nd a sparkgenerating apparatus, 'designated generally by the numeral i4 andenergized from the cathode circuit through a resistance 36 and a switch3,5. When the regulator is in operation a small amount of suitable, andpreferablyfinert gas is released into thea.l tube to return it to a softcondition, that is, raise the pressure therein.

An important feature of the invention by means of which uniformityv 'andconstancy pf excitation of the luminescent material and hence ,acorresponding uniformity and constancy of luminescence is obtainedresides in the use of the conducting surfaces i8* and 1 6 on theexterior andl interior walls of the -vessels over an area at leastco-extensivewithV the internal extension of the cathode '1. In additionto the above advantages,

the. use' of thesey conducting surfaces which are either grounded or maybe electrically connected to the cathode circuitgas illustrated, serveto materially increase the brilliancy andy uniformity of.

facesmay be either internal or external to the' vessel or both, and ifdesired, may be employed -at both ends of the' vessel, as will beillustrated later. These coatings may, vfor example, vtake the form ofactual metallic deposits upon the vessel walls as has been illustrateddiagrammatically in the drawings.rr It might be noted at this point thatthe current density relationship to the electrode areas is in no wayaffected and does not include the areas of, these coatings, except whenthe device is energized by strictly high frequency current.

L In order to prevent the accumulation of charges on the luminescentcoating, the container or support Ii therefor is ypreferably grounded orconnected-to some part of the circuit or to a special circuitcombination such as .illustrated in Fig.y 2 as involving the Wire id andthe resistance 20 shunted by capacitance 2i. Tofurther aid in theremoval of these charges should they accumulate, the coating itself mayhave mixed therewith conductive material, such as a metal powder, asillustrated4 at Dlil in Figure 2. 'I'he drain circuit if not grounded ispreferably connected into the anode circuit and includes the impedances2 2i to impart the proper impedance to this drain circuit. At this pointit may' be noted that the construction of Fig. 3 merely illustratesanother way of increasing the conductivity of the luminescent materialand of A mounting it upon and holding it on `a support. At 24 isillustrated a ne metallic screen or wire mesh into which the coatingmaterial .23 is pressed.

In order to take advantage of the fact that atelevated temperatures theluminescent material is often more active, a heating coil 25 is imbeddedin the insulating support 26 upon which the container ii is mounted.This heating coil may be energized through the external circuit 30 andthe control switch 28. 'Ihe temperature ,variation-is dependent upon thenature of the materials and the limits in either direction are likewisedictated. by the results secured.

It has also been discovered that the application of an intensel electricfield for a short period of time to the luminescent materlalin somecases enhances its intensity of luminescence. In other cases continuedapplication of this eld results electric field f a desired frequency` vIn the arrangement of Fig. 2 the various features as emphasized areshown in combination, but it will 'be apparent that in any particulardevices these various features Ymay `be used independentlyof each tions.

In Fig. 4 has been illustratedA a hot cathode type of deviceinaccordance with this invention. 'I'he vessel 3i with a suitableatmospheric cntent Yhas mounted therein a. cathode 32 in the other ortin desired combina- 'l form, for example, ofxa filament or indirectlyheated cathode of suitable shape, which may be energized fron'ianysuitable current source. This cathode is surrounded with a metallic-shield 31 having a function similar to the coatings I 6* and Iiib ofFig. 2. The luminescent coating assembly is substantially as previpuslydescribed, and need not be further discussed. In this case the metallicmember I1 carrying the luminescent coating I functions as anode in theusual circuit.

In the operation of a device of this type the adapted to be connected bywire 38 to a suitable potential source in' order to neutralize the spacecharge effect. An advantage of 'a structure of this type resides in thefact that it may be operated with a relatively low potential on theanode of the order of a few hundred volts, or even as low as the usualhouse lighting circuit voltage. In some cases the introduction of asuitable gas, preferably inert, into the hot cathode type of tube,increases the intensity of luminescence of the layer I0, which actionmay be further intensified by increasing the applied voltagewithinmaximum limits that are not too high to cause disintegration ofthe hot cathode.

It is, of course, apparently within the scope of this invention to makethe coating I0 of any one of a number of suitable materials or acombination of them, either in juxtaposition upon the support or inmixture, to give any desired design and color effects. By means of thisinvention, as will be further illustrated, the areas of the designs maybe greatly increased beyond anything herefore practical, becauseY of thefeatures of construction employed. It is likewise clear' that under theterm luminescent material it is intended to include both fluorescent andphosphorescent substances. Likewise, as lis well known; there are manyliquids which are'either fluorescent or phosphorescent under theexcitation of cathode rays, and hence may be employed as luminescentmedia in connection with devices of this type.

' A practical form of device in accordance with this invention, andwhich has been successfully operated for a considerable period oi' timeis illustrated in Figs. 5 and 6. It comprises a closed vessel 4I| havinga rarefled atmosphere of suitable gases and provided with an extension4i forming a smaller chamber and connected with the vessel45 by means ofa restricted neck 42..

The. chamber 4| is provided with a re-entrant.

which is sealed at its inner end and open at its A outer end to theanode chamber.

non-conducting material such as glass, and is further supported withinthe larger vessel by,

means of the pinches 55. At the other end of the vessel is the coldcathode 5I which may be eithercircular or rectangular in form and ispreferably made of a thin sheet of suitable metal such tas previouslyset forth. 'I'he cathode is provided with a central crease or bendso-that its projected area will coincide with both sides of the screen.ByV this construction the cathode rays which depart from the cathodealong lines perpendicular thereto will 'be directed over the display andfull wave rectifying device.

Supported on the stem 45 is a metallic entire surface of' the screen.The luminescent material 54' on one or bothsides of the screen is thussubjected to direct impact by' the cathode rays uniformly over itsentiresurface.

The cathode end of the tbe is likewise provided with the external andinternal coatings 55 and 55 which are at least co-extensive with thecathode. As illustrated in Fig. 5 all coatings are connected to therespective electrode circuits. The terminals of the secondary 52 of ahigh voltage transformer are connected to the anode and the cathode.vThe primary of the transformer is illustrated at 53. This device is acombined halfway rectier and display device. When the anode is positiveand the cathode is negative cathode rays will be generated and projectedover the entire area ofthe screen. When the anode becomes negative andthe cathode positive, current flow is interrupted. Actual-experience hasshown the device after initial ageing capable of the generation of highintensity luminescence of great uniformity and without flickeringorvfiuctuation. A device` of this type will not operate satisfactorilyon ordinary cycle current. For this reason a rectifier is essential, andin accordance withl this form of structure the rectifier is embodied asa partof the device. If necessary', in order to maintain uniformpressure conditions within the vessel I0, a side chamber 54 is providedcontaining a vapor or gas generating substance 55 which may be heatedbymeans of the heating coil 55. To make this structure automatic athermostatic device 51 isconnected in the heater circuit and subjectedto temperature or current fluctuations of the main device so that theheating coil will be switched on and off as necessary to maintain thepressure in the main device.

The structure of Fig. 7 involves a combined In this case the vessel 50is provided withthe screen 5I which supports the luminescent material.At each endof the vessel are the cathodes 54 shaped to project thecathode rays onto the screen. The anode 53 is mounted in a sidechamberand is connected to the electrical midpoint of the secondary 55, theterminals ofwhich are connected to the cathodes. At 51 is the energizingprimary; No discussion is necessary to illustrate the operation of thedevice as a full wave rectifier.

Another structure for accomplishing similar results is illustrated inFigs. 8 and 9. In this case the vessel 68 is of oval cross-section,illustrating that the transverse dimensions of the tube may ,be reducedwhere desired. Within the vessel is the screen 55 for supporting the,luminescent material. At I0 is the cathode, which lin this case may betermed a sort of roof, which extends.

along the top of the screen and is bent so as to direct the cathode raysover the entire surface of both sides'ofjthe screen. In this case a pairof l anodes 1I, 12 are provided which would be connected to thesecondary ofthe transformerv while t'he cathode 15 would be connected tothe midpoint thereof. Here again'the side tube 13 is supplied to hold agas generating substance vwhich may be heated asdesired by the heatingcoil 14 'through the thermostatically controlled circuit by discussedabove. The dimensions of said anode 75x are proportioned in accordancewith current density variations previously described.

The form of the invention as illustrated in Fig.

. is that of a long tube of relatively small diameter somewhat likethatof the luminescent gas discharge devices now employed for advertisingpurposes in the form of designs, letters, devices, and the like. Asshown it comprises a long glass tube 80 formed'into an airtight vesseland having a rareed atmosphere in accordance with the principlespreviously described. The vessel has a re-entrant stem 8l in which oneend of the cathode B2 is supported. The other end of this cathode passesthrough a seal in the opposite end of the vessel and to which electricalconnections can be made. .The cathode inthis case is in the form of alongv rod of suitable proportion. At 83 is an anode sealed into thevessel and exposed to the interior thereof through the openings 8f3 inthe re-entrant stem 8l. At 85 is shown the luminescent coating which inthis case is deposited upon the. interiorV wall of the vessel 80 so asto sur-` round the cathode 82 and to form, so to speak, a thin coating.The coating in this case, which may be of any one of the knownluminescent materials or desired mixtures thereof, is preferably verythin or else made in the form of a discontinuous surface so that whenthe material isexcited by the cathode rays the light generated may betransmitted therethrough so as to be observed from the exterior of thevessel.

This tube, although illustrated as a straight cylinder in the drawings,may, of course, assume any desired shapes andv sizes and may be formedup into letters, symbols, devices, or other display forms.

The structure of Fig. l1 comprises a domeshaped vessel 86 having are-entrant stem 8l! in which is supported the curved cathode 88. At 89are a pair of anodes mounted in smail chambers open to the interior ofthe main vessel. The pper dome-shaped portion of the vessel 86 isprovided with a coating 90 of luminescent material which mayVas statedbefore, beelther extremely thin or in the form of a discontinuoussurface so that iight may be transmitted to the exterior of the vessel.'

In all of these modifications it will be apparent that the -generalprinciples above described in detail, as well as the materials employedand the various circuit connections, may be used therewith to attain theimportant objects of uniform excitation of the luminescent coating. Furithermore, the current conditions of operation and the features ofrectification previously described may likewise be employed inconnection therewith.

It will be apparent to `those-skilled in the art that this inventionresides in certain principles of construction and operation which may beemplayedy in other physical forms. I do not, therefore, desire to bestrictly limited to the disclosure as given for purposes ofillustration, but rather to the scope of the appended claims.

What I seek to secure by United States Letters Patentis- Y 1. In aluminescent device, a sealed vessel having a rareed atmosphere, aluminescent substance supported within the vessel, means for excitingsaid substance, comprising any anode and a cathode, and conductivesurfaces surrounding the anode andthe cathode and in electrical contacttherewith.

2. The combination described comprising a closed vessel having a rareedatmosphere, a

comprising a closed vessel having a rarefied atmosphere therein, a lm ofluminescent material lsupported within said vessel, a cathode and ananode within said vessel positioned so as to project cathode raysuniformly over the surface of said film, and conductive shieldssurrounding the cathode and the anode and connected thereto for`increasing the uniformity of excitation of said film.

4. The combination as described comprising a closed vessel having arareed atmosphere, a cathode and an anode for said vessel, a.luminescent substance supported within the vessel so as to be betweenthe electrodes and in the dark space region of the discharge, and meanscontrolled by the current for operatingthe device for controlling thepressure lin the vessel to render the operation ofithe device morestable.

5. A luminescent light s ource of the type described comprising a closedvessel having a rarefled atmos'phere, a cathode and an anodesupluminescent substance. supported between thev cathode and the anode,and conducting shields surrounding the cathode and anode and extendingin an axial direction a distance suflicient to substantially surroundthe cathode and the anode and connected thereto respectively whereby theelectron discharge between the electrodes is uniformly distributed oversaid coating to effect uniform excitation thereof.

6. A luminescent light source of the type described comprising a closedvessel having a rarefied atmosphere, said vessel having a sealedreentrant stem forming an anode chamber and having an aperture in thewall ,thereof establishing communication between the chamber and vessel,an anode supported in said chamber, a cathode mounted in said vessel andspaced from said anode, a body of luminescent material supported betweenthe cathode and the anode, and means comprising conducting shieldsconnected respectively to the anode and the cathode for causing uniformdistribution ofthe discharge between the electrodes over the surface ofthe.

comprising a closed vessel having rareed at mosphere, an anode and acathode supported in said vessel, means forming a layer of luminescentmaterial supported between the anode and the cathode, means forming witha portion of said vessel a restricted chamber inl which said anode issupported, and a source of alternating current connected to the cathodeand the anode whereby the cathode and anode cooperate to produce arectifier for producing a rectified current which is applied to thecathode and anode to excite the cathode to produce an electron dischargevwhich is projected over the surface of said luminescent layer to exciteit.

8. A device of the type described comprising a closed vessel having arareed atmosphere,a cathode, an anode of small area-compared with thatof the cathode positioned in an adjoining chamber of the main vessel ofrestricted volume, a screensupported between the electrodes and in thedark space region of the discharge, and

l an alternating current supply source connected to said cathode andanode whereby the alternating current is rectified and applied to theelectrodes so that said coating is excited to luminescence.

9. A device of the type described comprising a closed vessel having arareiled atmosphere, cathodes in said vessel, a plate supported thereinsubstantially between the electrodes and in the free electron region ofthe discharge having a luminescent coating on both faces, said cathodeshaving such a geometric shape as to *project Y in adjoining extensionsof the main vessel, said coating lying substantially between theelectrodes and in the dark space region of the discharge.

11. The combination described comprising a closed vessel having arai'eiled atmosphere, a

cathode and an anode for saidvessel, a luminescent substance supportedwithin the vessel, substantially between the electrodes and inthe freeelectron region, so as to be excited by the rays generated by thecathode, and means for maintaining the pressure of the rareed atmosphereto render the excitation of the luminescent substance substantiallyconstant.

12. In a luminescent device the' combination comprising a closed vesselhaving a rareiied atmosphere therein, a surface of luminescent ma^terial supportedsubstantially between the electrodes and in the freeelectron region of the discharge within said vessel, an anode placed inan adjoining extension of the main vessel, and a cathode having such ageometric shape as to project cathode rays uniformly over the entirearea of the surface covered with luminescent material.

13. A luminescent light source comprising a closed vessel having arareed atmosphere, an anode and a cathode supported in said vessel inspaced relation, and means having a luminescent coating `supportedsubstantially between the anode and the cathode and in the freeelectronl region of the vessel, the cathode being shaped and lpositionedwith respect to the luminescent coating whereby electrons projectedtherefrom are uniformly distributed over the entire surface of thecoating.

ARSENE N. LUCIAN.

